Arsenic and Mesa's Water

Your water contains low levels of naturally occurring arsenic, but is in full compliance with current Environmental Protection Agency (EPA) standards. The EPA has set a new standard for arsenic at 10 parts per billion (ppb) to better protect consumers against the effects of long-term, chronic exposure to arsenic in drinking water.

The new standard applies to all 54,000 community water systems. A community water system is a system that serves 15 locations or 25 residents year-round, including most cities and towns, apartments, and mobile home parks with their own water supplies. The City of Mesa is evaluating several technologies for reducing arsenic concentrations.

Arsenic Occurrence

Arsenic occurs naturally in rocks, soil, water, air, plants, and animals. It can be further released into the environment through natural activities such as volcanic action, erosion of rocks, forest fires, or through human actions. Approximately 90 percent of industrial arsenic in the U.S. is currently used as a wood preservative, but arsenic is also used in paints, dyes, metals, drugs, soaps, and semi-conductors. Agricultural applications, mining, and smelting also contribute to arsenic releases in the environment.

Higher levels of arsenic tend to be found more in ground water sources (well water) than in surface water sources (i.e., lakes and rivers). Compared to the rest of the United States, western states, including Arizona, have more systems with arsenic levels greater than 10 ppb. Arsenic levels in Mesa's 38 wells range from 4 - 33 ppb.

For more information about Arsenic
Please contact the Water Quality division at 480-644-6461.